[资料分享] 《人工智能实践教程——从Python入门到机器学习》之运算符与循环

lijinlei 2024-8-11 23:33 楼主

# 人工智能实践教程

## 从Python入门到机器学习

### 运算符与循环

Python 通过缩进来组织代码，这里需要强调，在循环语句中，不同缩进往往对应循环结构体的不同位置，如

```python
# break continue
count = 1
sum = 0
while count <= 100:
  sum = sum + count
  if sum > 1000:
  break
  count = count + 1
print(sum)
```

### 运算符

包括各种运算符号的级别优先顺序，如加减乘除、比较符号、括号等，通过具体示例提升读者对运算符号及其使用规则的认识。

```python
# 2024-08-11
results = 59
if results >= 60:
  print("pass")
else:
  print("failed")

num = 6
if num:
  print("Hello Python")
# if 语句包含多个判断条件的形式
results = 89
if results > 90:
  print("Excellent")
elif results > 80:
  print("Good")
elif results > 60:
  print("Pass")
else:
  print("Failed")

# if 语句多个条件同时判断
java = 86
python = 68
if java > 80 and python > 80:
  print("Excellent")
else:
  print("General")

java = 86
python = 68
if (80 <= java < 90) or (80 <= python < 90):
  print("Good")

# Exercise 1.1
account = 100
if account > 500:
  print("Purchase Land Rover")
elif account >100:
  print("Purchase BMW")
elif account > 50:
  print("Purchase Magotan")
elif account > 10:
  print("Purchase Ford")
else:
  print("Purchase BYD")

# Exercise 1.2
# score_str = input("Enter your score: ")
# score = float(score_str)
score = 75
if score == 100:
  print("Car")
elif score >= 90:
  print("MP4")
elif score >= 60:
  print("A book ")
else:
  print("Nothing")

```

### 循环语句

该章节介绍了 for 和 while 循环的使用方法，同样结合具体实例，通过代码编写令读者掌握初步的和常见的使用方法和规则，为后面更加复杂的编程作铺垫。

```python
# 循环语句
# for 循环
for letter in "www.ecnu.edu.cn":
  print(letter)

for value in range(1, 6):
  print(value)

# while 循环
count = 1
sum = 0
while count <= 100:
  sum = sum + count
  count = count + 1
print(sum)

# break continue
count = 1
sum = 0
while count <= 100:
  sum = sum + count
  if sum > 1000: # when sum >1000 jump out of the loop
  break
  count = count + 1
print(sum)

# continue
count = 1
sum = 0
while count <= 100:
  if count % 2 == 0: # when count is even number jump out of the loop
  count = count + 1
  continue
  sum = sum + count
  count = count + 1
print(sum)

# while ... else
count = 0
while count < 5:
  print(count)
  count = count + 1
else:
  print(count)

# 嵌套循环
for num in range(0, 20):
  for i in range(2, num):
  if num % i == 0:
    j = num / i
    print('%d is a composite number' % num) # 合数
    break
  else:
  print('%d is a prime number' % num) # 质数

# 随机数
import random # 导入随机数模块工具包
random.randint(12,20) # 生成随机数，范围 [12,20]

# 猜数字
import random
smaller = int(input("Enter the smaller number: "))
larger = int(input("Enter the larger number: "))
myNumber = random.randint(smaller, larger)
count = 0
while True:
  count += 1
  userNumber = int(input("Enter your guess: "))
  if userNumber < myNumber:
  print("Too small")
  elif userNumber > myNumber:
  print("Too large")
  else:
  print("You've got it in", count, "tries!")
  break

```

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